The invention relates to a zoom lens that is compact and performs high magnification.
Optical imaging devices such as digital cameras or digital camcorders that use image pickup devices, such as charge coupled devices (CCDs) or complementary metal-oxide semiconductors (CMOSs), are widely used. These devices may require compact zoom lenses that have high performance and high magnification.
A lens having three lens groups, namely, a negative lens group, a positive lens group, and another positive lens group, is generally used to satisfy the need for high magnification and miniaturization. However, several difficulties exist in increasing zoom magnification and also securing high performance such as aberration correction or the like.
For example, if the number of lenses in the second lens group is increased to 4 or more, chromatic aberration may be easily corrected, but attaining zoom magnification is difficult and formation of an ultra-compact zoom lens is difficult due to the large number of lenses. Moreover, although a zoom lens designed to form a high magnification of 5× or greater has been proposed, miniaturization of the zoom lens is difficult due to a large change in a distance between the second lens group and a third lens group occurring during zooming from a wide angle position to a telephoto position.
In general, either miniaturization or cost-reduction is sacrificed in many cases to accomplish high optical performance and high zoom magnification. Accordingly, various design techniques capable of achieving both the miniaturization and the cost-reduction have been developed.